Extended chain polyethylene and extended chain polypropylene fibers of extremely high tenacity and modulus values are known materials, having been described by various publications of Professor Pennings and co-workers, Smith and Lemstra, and in certain copending commonly assigned patent applications of Kavesh, et al. These mechanical properties are due, at least in part, to the high degree of crystallinity and orientation imparted to the fiber by the production processes, which include either drawing an ultrahigh molecular weight polyolefin from a supersaturated solution or spinning a hot solution of the ultrahigh molecular weight polyolefin through a dye to form a gel fiber. Subsequent processing, including especially a stretching step, impart a high crystallinity and orientation to the polyolefin.
Unfortunately, such extended chain polyolefin fibers have two disadvantageous properties that result directly from a high crystallinity and orientation. First, the high orientation in the longitudinal direction gives the fibers extermely low transverse strengths, with a corresponding tendency of the fibers to fibrillate especially when subjected to abrasion or self-abrasion, particularly when twisted or processed into a fabric. This fibrillation is an undesirable feature in many applications, such as rope, sutures or fabrics. A second disadvantageous property of the extended chain polyolefin fibers is that their crystallinity causes these fibers to have poor adhesion to most matrix materials. This tends to limit the usefulness of these fibers in composite structures.